A typical commercial ambient cure epoxy coating contains condensates of dimer acids with polyethylene polyamides containing more than 4 amine hydrogen atoms as a curing agent and a solution of a solid epoxy resin. This epoxy coating system has excellent flexibility, adhesion to many substrates, and resistance to water and many types of solvents. However, a problem with this system is that a solvent content of almost 50% is necessary in order to obtain a "sprayable" (Gardner D or lower) viscosity. A large fraction of such solvent evaporates from a coating, or other exposed layer of epoxy resins during cure, and thereby behaves as a volatile organic compound (VOC). Environmentally it is desirable to have low VOC content.
Solvent requirements can be reduced considerably by using a system based on liquid epoxy resin with the above polyethylene polyamide curing agent. However, this approach tends to lead to coatings with low flexibility.
It is therefore an object of the present invention to provide epoxy coating systems which have good flexibility with reduced solvent requirements. Further, it is desirable to obtain epoxy systems for secondary containment membranes with increased tensile elongation with no losses, or minimal losses, in tensile or tear strength. It is also desirable to obtain epoxy systems for composite and adhesive applications with both increased tensile elongation and increased tensile strength and modulus as compared to current systems.